1. Field of the Invention
The present invention relates to a laminating film constituted of a base material and an image-protection layer for protecting a printed image by lamination, and also relates to a lamination process for protection of a printed image using such laminating film. In particular, the present invention relates to a laminating film suitable for forming an image protection layer on a printed image by transferring the image protection layer from the base material of the laminating film by hot-pressing the image protection layer onto an image surface and peeling off the base material from the image protection layer, and also relates to a lamination process for protecting the image using the laminating film.
2. Related Background Art
Methods are known for completing an image formed by electrophotography or ink-jet printing in which a transparent resin layer provided on a base material is transferred by thermocompression bonding with the base material either peeled off or kept unpeeled for improvement of the smoothness or glossiness of the image. Such methods are disclosed in Japanese Patent Application Laid-Open Nos. 06-091767, 2001-121609, and so forth.
Generally, a pair of hot-pressing rollers are used for the thermocompression bonding of the transparent resin layer. The hot-pressing rollers makes the lamination apparatus larger inconveniently.
On the other hand, techniques are known to impart durability such as abrasion resistance to thermally transferred images or the like, in which a resin is transferred onto an image by a sublimation-transfer system or a thermal transfer system, as shown in Japanese patent No. 2686657.
The inventors of the present invention investigated miniaturization of the lamination apparatus for convenience by making the heater assembly smaller by using a thermal head in place of the conventional heating rollers. Generally, the heat capacity of the thermal head is smaller than that of the heating rollers employing a halogen-heater or the like. Accordingly, the base material of the laminating film should be thinner to improve the heat conduction from the heater assembly for efficient bonding of the adhesion layer of the laminate onto the image surface by means of the thermal head.
However, the laminating film having a base material designed thinner tends to stick to the production apparatus or the delivery member of the film delivery system to cause failure in delivery or winding-up. To solve the problem with the thinner base material of the conventional laminating film or cover film, the surface is made coarse. As the results of investigation by the inventors of the present invention, when an printed image formed by electrophotography or ink-jet printing is covered by lamination with a protection layer formed on a surface of a thin and rough base material, the roughness of the base material is transferred to the surface of the protection layer to cause irregular light reflection at the protection layer surface to render the entire image hazy and to significantly lower the optical density to deteriorate the image quality of the laminate, even though the water resistance, gas resistance, and light fastness are improved by the protection layer. In particular, image quality can be deteriorated by irregular reflection especially in high density regions of the original image (image before the lamination treatment). This is a serious problem in obtaining an image having a wide density-expression range like a photograph.
An object of the present invention is to provide a laminating film which has a thin base material processable with a low energy and a protection layer capable of giving a high optical density and a high glossiness to a printed image by lamination, and also to provide a process for lamination with the laminating film.
Another object of the present invention is to provide a laminating film for ink-jet prints and electrophotographic prints, particularly for ink-jet prints having a porous surface, and to provide a process for lamination employing the laminating film.
A further object of the present invention is to provide a highly light-resisting laminating film, and to provide a lamination process employing the laminating film.
After comprehensive investigation to solve the above problems, the inventors of the present invention completed the present invention.
The laminating film of the present invention comprises a base material, and an image protection layer formed on the base material and having at least an adhesion layer capable of adhering to an image surface, wherein the base material has a thickness ranging from 1.5 to 6.0 xcexcm and has an arithmetic average roughness (Ra) of not more than 50 nm and a ten point height of roughness profile (Rz) ranging from 1200 nm to 2000 nm according to JIS B0601.
The lamination process of the present invention for laminating the image protection layer to an image surface of a printed product comprises the steps of
(i) providing the above-described laminating film,
(ii) bonding the adhesion layer of the laminating film onto the image surface of the printed product under heating, and
(iii) peeling off the base material, from the image protection layer after step (ii).